Fortran is completely new for me, can anybody help me to solve the follwing problem? I want to find out all the integer kind numbers and the largest and the smallest value for each kind number on my pc. I have code listed below:
program intkind
implicit none
integer :: n=1
integer :: integer_range =1
do while(integer_range /= -1)
print*, "kind_number ", selected_int_kind(n)
call rang(integer_range)
n = n *2
integer_range = selected_int_kind(n)
end do
contains
subroutine rang(largest)
integer largest
print*, huge(largest)
end subroutine
end
The integer kind numbers what I get are : 1,2,4,8.
Why is each largest integer for each kind number the same: 2147483647
? And is there a intrinsic function for the smallest integer?
How can I keep the integer kind number when the subroutine rang
is called? I think it is the key to the largest integer.
Your subroutine:
subroutine rang(largest)
integer :: largest
print *, huge(largest)
end subroutine
takes as input a default-sized integer, and prints the largest possible value that will fit in that default-sized integer. It will always return huge(default integer) which is, on most systems, huge(4-byte-integer), or 2147483647. huge
considers only the variable type; it doesn't interpret the variable in any way. The only way you could do what you're trying to do above is with parameterized derived types, which are new enough that support for it in compilers is still a little spotty.
If you want to take a look at ranges of different KINDs of INTEGERs, you'll have to use different variables:
program integerkinds
use iso_fortran_env
implicit none
integer :: i
integer(kind=int8) :: i8
integer(kind=int16) :: i16
integer(kind=int32) :: i32
integer(kind=int64) :: i64
integer(kind=selected_int_kind(6)) :: j6
integer(kind=selected_int_kind(15)):: j15
print *,'Default:'
print *, huge(i)
print *,'Int8:'
print *, huge(i8)
print *,'Int16:'
print *, huge(i16)
print *,'Int32:'
print *, huge(i32)
print *,'Int64:'
print *, huge(i64)
print *,''
print *,'Selected Integer Kind 6:'
print *, huge(j6)
print *,'Selected Integer Kind 15:'
print *, huge(j15)
end program integerkinds
Running gives:
$ ./intkinds
Default:
2147483647
Int8:
127
Int16:
32767
Int32:
2147483647
Int64:
9223372036854775807
Selected Integer Kind 6:
2147483647
Selected Integer Kind 15:
9223372036854775807